title: Diverse synthesis of marine cyclic depsipeptide lagunamide A and its analogues.
abstract: The asymmetric total synthesis of lagunamide A (3.0%, 20 steps longest linear sequence) and its five analogues, including the structure dehydrated at the C37 position, are detailed in this report. The key feature in this diverse synthesis includes the elaboration of four consecutive chiral centers at C37-40 and the final macrocyclization. Starting from chiral aldehyde 10, we synthesized both 1,3-anti and 1,3-syn homoallylic alcohols 20a and 20b through asymmetric aldol condensation and stereoselective allylation. The following esterification to introduce the L-N-Me-Ala unit resulted in significant epimerization. This problem was finally overcome by coupling the alcohols with the corresponding acid chloride of the L-alanine derivative. The key α,β-unsaturated carboxylic acid unit was produced by cross-metathesis (CM) of methacrylaldehyde and related olefins. Interestingly, we found that the C7 configuration dramatically affected the ring closure. Natural lagunamide A (1a), its 39-epimer (1c), and its 2-epimer (1d) were obtained through macrolactamization between alanine and isoleucine moieties.
authors.affiliation: Department of Chemistry and Institutes of Biomedical Sciences, Fudan University , 220 Handan Road, Shanghai 200433, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Rong-Guo
authors.initials: RG
authors.lastname: Ren
authors.forename: Han-Qing
authors.initials: HQ
authors.lastname: Dong
authors.forename: Bang-Guo
authors.initials: BG
authors.lastname: Wei
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Lin
mesh_terms: D000409:Alanine / Q000737:chemistry*; D047630:Depsipeptides / Q000138:chemical synthesis* / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D047630:Depsipeptides; C554215:lagunamide A; D000409:Alanine